D. Covarrubias¹, A. Méndez², & C. Vargas³

¹ CICESE Research Center, Km. 107 Carretera Tijuana-Ensenada Ensenada, Baja California, 22860 México, Phone: (52) 646.175.0555, Fax: (52) 646.175.0554 e-mail: dacoro@cicese.mx

² Autonomous University of Tamaulipas, UAT-UAMRR Carretera Reynosa-San Fernando, Reynosa, Tamaulipas, 88779, México. Phone: (52) 899.921.3300, Fax: (52) 899.921.3301 e-mail: almendez@uat.edu.mx

³ ITESM-CET Campus Monterrey, Ave. Eugenio Garza Sada 2501 Sur CETEC 7o piso TS Monterrey, Nuevo León, 64849 México. Phone (52) 818.158.2081, Fax: (52) 818.359.7211. e-mail: cvargas@itesm.mx

Received: December 10^th, 2002. ]]> Accepted: February 24^th, 2005.

Abstract

This paper evaluates the effects of Rayleigh fading, shadowing, and spatial distribution of the Mobile Terminals (MTs) on the operating performance of Slotted Aloha (S-Aloha) used as a Random Access Channel (RACH). This paper also evaluates the capture probability in a channel exhibiting Rayleigh fading, shadowing, and the effect of spatial distribution of the MTs. In addition, this work presents a different version of the steady-sate probabilities of the Markov chain of S-Aloha considering capture effect. This article simulates the stabilization of S-Aloha by utilizing an algorithm that dynamically controls the retransmission probabilities. Finally, this paper presents a numerical analysis of these simulations and identifies the operating of parameters that have shown to degrade system response.

Keywords: Mobile communications, Capture effect, Retransmission algorithm, S-Aloha stability.

Resumen

Este artículo evalúa las prestaciones de Aloha ranurado (S-Aloha), usado por el terminal móvil en la fase de petición de canal aleatoria, considerando los efectos de desvanecimiento Rayleigh, sombreo y distribución de los terminales móviles. También evalúa la probabilidad de captura en un canal exhibiendo desvanecimiento Rayleigh, sombreo y distribución espacial de los móviles. Además, se presenta una versión diferente de las probabilidades en estado estable con efecto captura de la cadena de Markov de S-Aloha. Por otro lado, se simula la estabilización de S-Aloha, empleando un algoritmo que controla dinámicamente las probabilidades de retransmisión. Por último, se lleva a cabo un análisis numérico de los resultados y se identifican aquellos parámetros que degradan la respuesta del sistema de comunicaciones móviles celulares.

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